There has been used a plating method for forming wiring on a substrate. However, since an opening dimension of a wiring groove or hole formed on a substrate becomes smaller to meet the recent demands for high integration of devices, plating solution cannot be supplied into the opening in the conventional plating method so that it makes difficulty in forming wiring.
Hence, there has been examined a method for forming wiring by a CVD (Chemical Vapor Deposition) method described in, e.g., Patent Document 1, instead of the plating method. In this method, a metal film is formed by causing a chemical reaction of a source gas on a substrate, the source gas being produced by sublimating a liquid source material of, e.g., metallic organic complex. Similarly, in the case of using a solid source material, a solid source material is sublimated to produce a source gas. Further, in this method, in order to form a film with high in-plane uniformity, the film formation is performed in a processing chamber while maintaining the processing chamber in a vacuum state by exhausting therein. Moreover, the source gas is used in a state of being diluted to ppm-levels with, e.g., Ar gas or the like.
In the vacuum state, a source gas concentration and a film forming rate decrease. In order to increase a throughput of the film formation, the film forming rate needs to be increased, and this requires a large supply amount of the source gas. Since, however, most of the source gas is exhausted, the use efficiency of the source gas that contributes to the film formation is only a few percent. The unnecessary waste of large amount of the source material is cost-ineffective due to its high cost, and hinders effective utilization of the source material.
Further, the CVD apparatus requires a high-volume vacuum pump capable of exhausting a large amount of source gas despite that such vacuum pump is considerably high-priced. Moreover, a large exhaust amount of the source gas that produces deposits or products accelerates deterioration of the vacuum pump by the source gas, which increase the maintenance cost. For such reasons, there is required a film forming apparatus capable of reducing waste of a source material and performing cost-effective film formation.
Patent Document 2 describes a technique for liquefying a source gas on a substrate. However, this technique cannot solve the problems of the present invention.
Patent Document 1: Japanese Patent Laid-open Publication No. 2006-299294 ((0021)-(0026))
Patent Document 2: Japanese Patent Laid-open Publication No. 2004-047644 ((0024)-(0028))